1. Field of the Invention
The present invention relates to electric motors generally and, more particularly, but not by way of limitation, to a novel integral shaft beating and bobbin structure for electric motors.
2. Background Art
Although electric motors have a variety of configuration, many electric motors, and, particularly, rotary stepping motors, typically include a rotating member, or rotory disposed for rotation within an annular stationary member, or stator, the stator comprising a coil of wire wound upon a bobbin. The rotor and the stator are fixed between end plates, with a rotor shaft attached to and extending from the rotor and journalled in bronze bearings pressed into the end plates.
An electric motor constructed as outlined above has a relatively high parts count and, therefore, is relatively expensive to construct. In addition, the multiplicity of parts can result in additive concentricity tolerances and, therefore, it can be difficult to achieve the required precise alignment of the upper and lower bronze bearings. Also, conventional bronze bearings tend to lose lubricity and can seize to the rotor shafts at low temperatures. As a countermeasure to the latter problem, larger tolerances are used; however, in some applications, such as when stepping motors are employed in bar code readers, the larger tolerances lead to "FIG. 8" scanning which can result in the misreading or the non-reading of bar codes.
Accordingly, it is a principal object of the present invention to provide a bearing structure for electric motors that is simple in construction.
It is a further object of the invention to provide such a bearing structure that eliminates or reduces the addition of concentricity tolerances during assembly.
It is an additional object of the invention to provide such a bearing structure that may be economically manufactured.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.